On Thu, Apr 29, 2010 at 6:50 PM, Stefan <mstefanro@gmail.com> wrote:
vicente.botet wrote:
----- Original Message ----- From: "Christoph Heindl" <christoph.heindl@gmail.com> To: <boost@lists.boost.org> Sent: Thursday, April 29, 2010 5:50 PM Subject: Re: [boost] [any] boost::get style accessors
On Thu, Apr 29, 2010 at 1:10 PM, Stewart, Robert <Robert.Stewart@sig.com> wrote:
Christoph Heindl wrote:
On Wed, Apr 28, 2010 at 8:00 PM, Stewart, Robert <Robert.Stewart@sig.com> wrote:
At that point, I think they should be on par with any_cast rather than built on any_cast so that exceptions needn't be translated. Exception handling overhead is too costly to do it twice when it isn't necessary.
I agree. I don't see any added value by using bad_get, except all boost:get accessors would throw bad_get exceptions.
Perhaps you missed my point. I was suggesting that your gets be implemented at the same level of access as any_cast so no exception translation were needed. In other words, take code straight from any_cast and use it to implement get, provided bad_cast is deemed useful.
Indeed I did. In boost 1.42 this corresponds to duplicating ~40 lines of code to exchange the type of exception thrown. I'm not too keen of doing this (not talking about the tests I would have to duplicate too) :) Of course, code could be refactored to refer to a common set of methods that take the exception to throw as templated argument, if desired.
_______________________________________________ +1 for refactoring. Best, Vicente
_______________________________________________ Unsubscribe & other changes: http://lists.boost.org/mailman/listinfo.cgi/boost
It would make little sense to have a boost::get working with both Boost.Variant and Boost.Any transparently if it does not have a consistent behavior (i.e. the same way of signaling a problem). I don't think refactoring some code to make the behavior consistent will be problematic.
Agreed.
Currently, boost::bad_get is deriving directly from std::exception whereas boost::bad_any_cast is deriving from std::bad_cast. It might make more sense to have both boost::bad_get and boost::bad_any_cast derive from a common exception class type, such as boost::bad_cast (or maybe have boost::bad_get derive from std::bad_cast)
I'd prefer to have boost::bad_get derive from std::bad_cast since it seems like a natural fit to me. However, I haven't taken other implementations of boost::get<T> and their exception handling into consideration where a bad_cast exception might not be appropriate (because nothing is to be casted). Thinking about this further, what about having a common exception for all boost::get (note the missing template argument), called bad_get that derives from std::exception. Additionally we add bad_get_cast as a specialization (i.e. derived from bad_get) for boost::get<T> where T correponds to either boost::any , boost::variant or any other T that requires casting internally. --Christoph